How Flip Works
Flip is a 50/50 game where the card is guaranteed but the price is variable. You pick a card, click Flip, and a provably-fair coin decides whether you pay less than market or more.
The math
Each Flip-eligible card has a spread set by the seller. The default is 25%.
| Term | Formula |
|---|---|
| Card value | Market comp price (set by seller) |
| Win price | cardValue × (1 - spread) |
| Lose price | cardValue × (1 + spread) |
Example: $100 card at 25% spread
| Outcome | Probability | You pay | Net vs. market |
|---|---|---|---|
| WIN | 50% | $75.00 | +$25 in your favor |
| LOSE | 50% | $125.00 | −$25 against you |
| Expected value | — | $100.00 | $0 (zero-sum) |
The expected value of a Flip is exactly the card's market value. Over a large number of plays, you'd expect to break even. Spreads vary by seller — wider spread = more volatility per play, same EV.
The play sequence
- Browse thisorthat.slabtrack.io → click a card you like
- You see: card image, win price, lose price, spread, and the SHA-256 commitment hash
- Click Flip → checkout opens. Stripe holds an authorization for the LOSE price (worst case)
- You confirm. The server generates a 32-byte random seed, deterministically computes WIN or LOSE from that seed, and adjusts the Stripe charge to the actual amount
- The result is revealed: WIN or LOSE, with the seed shown so you can verify
- Stripe captures only the actual amount (win or lose price)
- The card ships to your address within 24-48 hours
Stripe initially authorizes the LOSE price (the worst-case for you). If you WIN, the charge is reduced to the win price; the difference is released back to your card within 5-7 days. If you LOSE, the full lose price captures. Either way, you only ever PAY the actual outcome — but the auth on your statement may briefly show the higher number.
What "always ships" means
There is no losing outcome where you don't get the card. WIN = you bought it cheap. LOSE = you bought it pricey. Both end with the card in the mail to you. The only "lose" is paying above market. This is fundamentally different from a slot machine or a pack of trading cards.
What you can verify after
After the result is shown, click Verify. You'll see:
- The 32-byte server seed (in hex)
- The SHA-256 hash of that seed (this is what we committed to BEFORE you played)
- The Solana transaction ID where we anchored the hash
- The bit that decided your outcome (last byte of the seed, even = win, odd = lose)
You can paste the seed into any SHA-256 calculator and confirm it matches what we anchored. Full verification walkthrough here.
FAQ
- Is it gambling?
- Legally, no — you always get a tangible card with established market value, not a chance at a prize. Practically, the spread creates volatility similar to a market with a built-in spread. Read the spread carefully before you click.
- Can I see what the seed will be before I commit?
- No, but you can see the SHA-256 hash of the seed BEFORE you commit. After the reveal, you can verify the seed matches that hash. We can't change the seed after the hash is published — that's the cryptographic guarantee.
- What if Stripe declines my card?
- The play doesn't happen. No seed is committed, no result, no charge. You can retry with a different card.
- What if I already bought the same card on a Flip and want another?
- Each card is unique. Once one Flip resolves, that listing is gone. Other identical cards (same player, set, year) might be listed separately.